Process for the synthesis of ammonia

Abstract

Process for the synthesis of ammonia comprising the steps of reforming of a hydrocarbon feedstock into a raw product gas, purification of said raw product gas obtaining a make-up synthesis gas, conversion of said synthesis gas into ammonia; said purification includes shift conversion of carbon monoxide into carbon dioxide and the reforming process requires a heat input which is at least partially recovered from at least one of said step of shift conversion, which is carried out with a peak temperature of at least 450° C., and said step of conversion into ammonia.

The invention claimed is: 
     
       1. A process for the synthesis of ammonia comprising the steps of:
 reforming of a hydrocarbon feedstock into a raw product gas, said reforming requiring a heat input; 
 purification of said raw product gas obtaining a make-up synthesis gas; 
 conversion of said synthesis gas into ammonia, wherein said purification includes shift conversion of carbon monoxide into carbon dioxide, wherein said heat input of the reforming process is at least partially recovered from at least one of: 
 said step of shift conversion, which is carried out with a peak temperature of at least 450° C.; 
 said step of conversion into ammonia; and 
 wherein said heat input of the reforming process is at least partially recovered from the step of conversion into ammonia, and said heat recovery is carried out by: direct cooling of one or more catalytic beds for the synthesis of ammonia, and/or cooling an effluent of an ammonia catalytic bed or ammonia reactor. 
 
     
     
       2. The process according to  claim 1 , wherein heat of said shift conversion is recovered by either: direct cooling of a catalytic bed of a related shift converter, and/or cooling an effluent of shifted gas. 
     
     
       3. The process according to  claim 1 , wherein conversion into ammonia includes the reaction of make-up gas in a plurality of reactors or of catalytic beds in series, and heat is recovered by cooling the effluent of the first of said reactors or catalytic beds, before admission to the subsequent reactors or beds. 
     
     
       4. The process according to  claim 1 , wherein heat recovered from the shift conversion and/or from synthesis of ammonia is used to pre-heat a mixed feed including hydrocarbon and steam, before admission of said mixed feed to the reforming step. 
     
     
       5. The process according to  claim 4 , wherein pre-heated mixed feed is subject to pre-reforming before the reforming step. 
     
     
       6. The process according to  claim 4 , wherein:
 a mixed-feed of natural gas and steam is cooled by exchanging heat with another process stream; 
 the so obtained cooled mixed feed is then re-heated by cooling a shift reactor or the effluent thereof. 
 
     
     
       7. The process according to  claim 4 , wherein the mixed feed, prior to reforming, is preheated with a recovered heat and said recovered heat comes exclusively from cooling of an effluent of a high-temperature shift. 
     
     
       8. The process according to  claim 1 , wherein said reforming of the hydrocarbon feedstock comprises: a primary reforming with steam and a secondary reforming with an oxidant and optionally a gas heated reformer (“GHR”), or a step of auto-thermal reforming and optionally a GHR. 
     
     
       9. The process according to  claim 6 , wherein a mixed-feed of natural gas and steam is cooled by exchanging heat with a fresh natural gas feed before a desulphurization. 
     
     
       10. The process according to  claim 7 , wherein the mixed feed, prior to reforming, is preheated with a recovered heat and said recovered heat comes exclusively from cooling of an effluent of a high-temperature shift, wherein said effluent has a temperature after the high temperature shift of at least 450° C.